The Biogeochemistry of Lipid Derived Infochemical Signals in the Ocean

Bethanie Edwards, Ph.D., 2016Benjamin Van Mooy, Advisor

Oxylipins are lipid derived infochemicals produced by mainly by diatoms. The work presented in this thesis suggests that oxylipins production in situ has significant implications for ocean biogeochemistry. Oxylipin concentrations on sinking particles from the North Atlantic were in the micromolar range. Stimulatory concentrations of oxylipins ranged from 1-10 µM, resulting in enhanced remineralization of organic matter by particle associated microbes. Thus, PUAs produced during bloom decline may lead to greater flux attenuation and nutrient recycling.A novel lipidomics approach was applied along a cruise track in the California Coastal System revealing that free fatty acids and oxylipins dominated the dissolved lipidome were correlated with diatom bloom demise. RNA viruses were linked to bloom decline and oxylipin abundances, representing a new infochemical signaling pathway in the ocean.The dissolved lipidome was sampled during grazing experiments with the microzooplankton grazer Oxyrrhis marina and both wild type Phaeodactylum tricornutum and a chronically stressed, transgenic strain (PtNOA). Grazing was suppressed in the PtNOA treatments compared to the WT, likely due to upregulation of small unknown lipophilic molecules. This suggests that cellular stress and oxylipin production may deter microzooplankton grazing in the environment potentially altering the transfer of energy through the microbial food web.